Apparatus for esterification



A. A. BACKHAUS.

APPARATUS FOR ESTEBIFICATION. APPLICATION HLED'SEPT. 20, 19:9.

'Jl,%3,2?,5 Patented. Jam. 1ND, 19221,.

I 2 SHEETS-SHEET l.

ILA825 A. A. BACKHAUS.

APPARATUS FOR ESTERIFICATlON.

APPLICATION FILED SEPT. 20., 1919.

Patented Jan. 1111)., 1922.

2 SHEETS-SHEET l ll in I wvevvtoz UNHTJEID STATES ggraar OFFHCE'.

ARTHUR A. BACKHAUS, 0F BALTIMORE, MARYLAND, ASSIGNOR TO U. INDUSTRIAL ALCOHOL 00., A CORPORATION OF WEST VIRGINIA.

APPARATUS FOR ESTERIFICATION.

Specification of Letters Patent.

Patented Jan. 10, 11922.

Application filed September 20, 1919. Serial No. 325,108.

To all whom it may concern Be it known that I, ARTHUR A. BAOKHAUS, a citizen of the United States, residing at Baltimore, and State of Maryland, have in vented a certain new and useful Improvement in Apparatus for Esterification, of which the followingis a specification.

My invention relates particularly to an apparatus for producing esters having a high grade of purity by providing an effective method of esterification, but it relates especially to the production of ethyl acetate in this manner which is substantially free from alcohol.

The object of my invention is to provide an apparatus for esterification, by means of which the highest yields of esters may be obtained, and the object of my invention is furthermore to obtain esters in this way having a high degree of purity especially ethyl acetate of substantially 100% strength.

Another object of my invention is to provide such an apparatus in which the organic acid and alcohol are subjected to the action of a catalyst for the maximum period of time during which the esterification will take place, inasmuch as I' have discovered that there is a fixed period of time during which the treatment must continue in order to obtain the maximum esterification irrespective of the percentage of the organic acid present.

Further objects of my invention will appear from the detailed description thereof contained hereinafter.

lVhile my invention is capable of being carried out in many different ways, for the purpose of' illustration I have shown only one way of carrying out the same in the accompanying drawing, in which:

The figure is a diagrammatic representation of an apparatus which is made in accordance with my invention.

lVhile my invention is capable of being rarried out in connection with the mani1fac ture of different esters, and with the use of different starting materials, I shall by way of example describe the invention as applied to the manufacture of ethyl acetate from phuric acid.

In the drawing, I have shown two mixing tanks 1 and 2 which are designed to be used alternately, the construction of which is exactly'the same in the two tanks. The tank 1 is provided with three inlet pipes 3, 4: and 5 containing sulphuric acid, alcohol, and v1negar respectively. These three materials are fed into the tank 1 in the proportion of "33 parts by weight of sul huric acid having a strength of 50 to 66 to 10 parts by weight of vinegar having a strength of 8% acetic acid, and 8/10 part by weight of ethyl alcohol having a strength of 95%. These materials are mixed in the tank 1 by means of an agitator 6 driven from any suitable source of power. The mixed materials are fed out of the tank 1 into a valved pipe 7, from which they are discharged by a pump 8 through a pipe 9 into a supply tank 10. The mlxing tank 2 is also connected to the plpe 7 by means of a valved branch pipe 11, and it will be understood that in the operation of the apparatus the two mixing tanks 1 and 2 will be operated alternately. The pump 8 supplies these mixed materials to the supply tank 10 continuously, and there from they flow continuously by means of a valved pipe 12 through a combined dephlegmator and preheater 13, provided with tube sheets 14 and 15 and interposed tubes and is thus caused to pass througha descending current of the liquid passing over a plurality of pans 22 and 23 alternating with one another so as to enable pans 23 to act as storage pans while the pans 22 serve to cause the ascending vapors to pass through the bodies of liquid carried by the pans 22. In order to accomplish this, as shown in the drawings, there are located a number of vapor pipes 24 covered with hoods 24 while in the pans 23 there are vapor conducting pipes 24. The construction is such as to subject the alcohol and acetic acid to the action of the catalyst in the column for a length of time in any given instance in which the maximum degree ofesterification obtainable will havebeen reached. This length of time is dependent upon the percentage of alcohol present. If there is only 20% of alcohol presentthe time required is one half hour,

but if 60% of alcohol is present the time necessary will be one and one half hours. If the storage pans 23 were not provided in the column 20 the maximum esterification obtainable would not be secured as the alcohol and acetic acid would not be subjected in any one given instance in the column 20 to the action of the catalyst for this length of time. From the bottom of the column 20, the slop containing sulphuric acid is continuously discharged by a pipe 25 leading to an overflow bottle 26 having a vapor outlet pipe 27 leading back to the column 20 and a liquid discharge pipe 28 passing out from the bottom of the bottle 26. In the side of the column 20, there is also a further trapped inlet pipe 29 for feeding into the same alcohol having a strength of 70-90%,

which is supplied from a portion of the ap-- paratus to be hereinafter described. Through the action 4 of the catalyst ethyl acetate is formed in the column, and continually passes out of the top of the same admixed with alcohol and steam by means of the pipe 17 which is connected 'to the -dephlegmator and preheater 13. The lower portion of the vapor space in the dephlegmator and preheater is connected by the pipe 18. to the upper portion of the column 20, so as to convey back into the same the first distillate in order to kee the pans sealed in the col umn. From this point the vapors pass from the dephlegm'ator andpreheater by a pipe 30 to a warm condenser 31 having two tube sheets 32 and 33 connected with a series of tubes 34, and the temperature of which is maintained at 60-70 0., by a current of hot water passing into the same through inlet and outlet pipes 35 and 36. From this point the condensed'liquid which comprises approximately "20% by wei ht of ethyl acetate, 60% by weight of alco 01, and 20% by weight of water passes out of the condenser by means of a pipe 37 to a bottle 38 having a. valved trapped liquid'outlet pipe 39 and a vapor outlet pipe 40 which latter leads to a cold condenser 41 having tube sheets 42 and 43 provided with a series of interposed tubes 44 cooled by a current of water supplied through inlet and outlet pipes 45 and 46. The condensate from they condenser 41 passes by a pipe 47 into a bottle 48 having a Vapor vent pipe 49 and a trapped liquid outlet pipe 50 which leads to the liquid outlet pipe 39. From thepipe 39 a pipe 51 conveys any excess of the liquid not fed forwardly in the apparatus back to the pipe 18, so as to allow the same to be discharged in the column 20. This pipe 51 has an upwardly bent portion 52, so that only such excess will pass through the pipe 51. The ipe 39 conveys the mixed ethyl acetate, a cohol, and water, into a separating column 53, the interior of which is constructed the same as in the case of the column 20, except that in this instance the storage pans 23 are omitted and only pans like the pans. 22 are present and, furthermore, there is a steam heater 54 comprised of 3 tube sheets 55 and 56 carrying a pluralityof tubes 57. They upper portion of this column is maintained at a temperature of substantially C. In the side of the column 53, there are additional trapped liquid inlet pipes 58 and 59 leading from parts of the apparatus to be hereinafter described, and .at the bottom of the column. 53 there is an outlet pipe 60 leading to an overflow. bottle 61 connected by a vapor outlet pipe 62 to the column 53 and connected at its lower end to the pipe 29. The

vapors which pass out of the top of the column 53 are comprised of a mixture of ethyl acetate, alcohol, and water,the principal constituent of which is ethyl acetate.

These vapors are conveyed by a pipe 63 to adephlegmator 64 having tube sheets 65 and 66 carrying tubes 67 and provided with a trapped liquid returnpipe 68 leading back to the top of the column 53 in order to keep the pans therein sealed with liquid. The dephle-gmator 64'is cooled by a current of cooling water supplied with the aid of inlet and outlet pipes, 69 and 70. From this dc phlegmator 64 the uncondensed vapors pass by a pipe 71 to a condenser 72 having tube sheets 3 and 74 carrying tubes 75 and cooled by a current of water sup lied with the aid of inlet and outlet pipes 6 and 77.

The vcondensate which comprlses a constant boiling mixture of ethyl acetate, alcohol, and water, contains approximately 83% of ethyl acetate, 9% of ethyl alcohol, and 8% of'water, and is conveyed out of the condenser 72 by means of a pipe 78 to an overflow bottle 7 9 having a vent 80 and a valved liquid outlet pipe 81. From this outlet pipe 81 a pipe 82 is provided for conveying any excess of the liquid back to the pipe 68 and thence to the column 53, said pipe 82 being provided with an upwardly bent portion 83.

topermit only such excess to be fed 'in-this direction. The pipe 81 conveys this consteadof being led by the pipe 58 into the column 53. When the liquid in the pipe 58 contains at least 80% ester, it will be fed through the pipe 85 into the pipe 81,

but if the percentage of the ester is lower,

it will be fed instead by the pipe 58 back into the column 53. The measuring receptacle 84 has attached to the inlet pipe 81 therein a container 86 which discharges the liquid laterally near the inner periphery of the receptacle 84, and around the inlet pipe 81 there is located an outlet pipe 87 having a slot 88 with a scale 89 at the side thereof to indicate by the height of the level of the liquid in the receptacle 84 the speed of outflow of the liquid. The pipe 87 conveys this constant boiling mixture of ethyl acetate, alcohol, and water, to a mixing coil 90 which is supplied with water by means of a pipe 91 leading from a measuring receptacle 92 constructed in the same manner as the measuring receptacle 84, and which is continuously supplied with water by means of a valved pipe 93. From the mixing coil 90 these liquids pass into a separating chamber 94 where the. liquid separates into a lower water layer 95 containing small percentages of ethyl acetate, and alcohol, and an upper layer 96 containing approximately 94% of ethyl acetate, 4% of water, and 2% of alcohol. The lower layer containing the small percentage of ethyl acetate passes out of the separating chamber 94 by a vented overflow pipe 97 to the pipe 59, and thence back to the column 53. The upper layer of liquid 96 containing a higher percentage of ester flows out of the chamber 94 by a trapped pipe 98 into the side of a drying column 99. This column 99 is constructed on the interior thereof in the same manner as the column 53. The lower portion ofthe column 99 is maintained at a temperature of substantially 75 C. The vapors passing out of the top of the col umn 99are conveyed by a pipe 100 to a dcphlegmator 101 having tube sheets 102 and 103 carrying a plurality of tubes 104, and arranged to return the liquid therefrom by a trapped pipe 105 to the upper end of the column 99 in order to seal the pans therein. Said dephlegmator 101 is cooled in the usual. manner by means of a current of water supplied With the aid of inlet and outlet pipes 106 and 107. The uncondensed vapors pass out of the dephlegmator 101 by a pipe 108 to a condenser 109 having tube sheets 110 and'lll provided with tubes 112 and cooled by a current of water with the aid of inlet and outlet pipes 113 and 114. The condensate which will ordinarily comprise constant boiling mixtures of ethyl acetate, alcohol, and water, passes out of the condenser 109 by a pipe 115 to an overflow bottle 116 having a vent 117 and an outlet pipe 118. This outlet pipe 118 is connected by a valved pipe 119 to the pipe 105, so that when desired the liquid may be returned to the column 99 so as to avoid returning the liquidto the column 53 when the latter or some part associated therewith is to be thrown out of operation temporarily. Ordinarily, however, this pipe 119 will be closed and the liquid will be fed from the pipe 118 to the pipe 58, and thence either into the measuring receptacle 84 or the column 53 according to the composition of the liquid as above pointed out. From the bottom of the column 99 ethyl acetate having a' strength of 95 to 100% passes out by a pipe 120 to an,

overflow bottle 121 having a vapor outlet pipe 122 leading back to the column 99 and an outlet pipe 123 leading out of the bottom of the bottle 121. This pipe 123 conveys the ethyl acetate to a cooling coil 124 located in a cooler 125 cooled by a current of water supplied with the aid of inlet and outlet pipes 126 and 127. The cooled ethyl acetate passes away from the cooler 125 by means of a trapped pipe 128, and is collected in a storage receptacle 129 from which it may be drawn off from time to time, as desired, by a valved pipe 130.

The operation of my invention will be apparent from the above description. It will be understood, however, in general that to provide an excess of alcohol the tank 10 is in starting filled with alcohol, then the sulphuric acid, alcohol, and vinegar are mixed in the proper proportions hereinabove referred to in the two tanks 1 and 2 alternately, and that from these tanks the mixed materials are conveyed continuously to the supply tank 10 from which they are continuously conveyed through the preheater 13 to the esterification column 20, from the bottom of which the slop containing sulphuric acid is continuously discharged, while the vapors of ethyl acetate, alcohol, and water pass out of the top of the same to the preheater 13 which acts also as the dephlegmator, to return to the column 20 the first condensate. As previously pointed out the action of the esterification column 20 is such as to produce the maximum amount of esterification obtainable with the materials present inasmuch as the latter are subjected at any one point in the column 20 to the action f the catalyst for a sufiicient length of time to produce a maximum yield of the ester at this point, that is to say, ethyl acetate. Furthermore, the degree of esterification obtainable at any given point in the column 20 will depend upon the percentage of the alcohol in the materials present as above pointed out and in general the percentage of the organic acid that will be transformed into the ester at any given point in the column 20 will be approximately the same percent as the percentage of the alcohol contained in the material present. From the dephlegmator 13 the vapors pass into the hot condenser 31 and finally the cold condenser 41, so as to condense the vapors to a liquid with the minimum loss of heat, and thus obtain a mixture of ethyl acetate, alcohol and water in the form of a liquid prior to supplying the same to the separating column 53. It is highly desirable to condense these vapors to a liquid at this .point as otherwise owing to the low'latent heat of vaporization of the ethyl acetate present compared with the high latent heat of vaporization of the alcohol present, if

these materials were fed into the column 53 in uncondensed form,-'the ethyl acetate in the column 53 would'be vaporized to a disadvantageous degree because of the large amount of heat present. In the column 53 the ester is very largely separated from the alcohol, the alcohol being fed back into the 'esterification column while the ester and admixed remaining alcohol and water are obtained in the form of a constant boiling mixture which is thereafter intermingled with water in the coil 90, so as to form the two layer of liquid containing high and low percentages of ethyl acetate respectively in the chamber 94. The layer containingthe lower percentage of ethyl acetate is fed back into the separating column '53 while the layer containing the higher percentage of ethyl acetate is conveyed into the drying column 99 where the excess of the ester over the constant boiling mixture of ethyl acetate, alcohol, and water is drawn off at the bottom, passed through the cooler 125, and received in the storage receptacle 129, the constant boiling mixture being returned from the top of the column 99 either to the measuring receptacle 84 or the column 53. In this way, it is possible to obtain continuously ethyl acetate having a strength of 95 to 100% according to the operation of the apparatus.

It will be understood that other acids and other alcohols may be used instead of the provided with a vapor pipe and a hood with the aforesaid plates, each provided with apertures, with a comparatively high tube or cylinder therein and pipes connecting the plates to let liquids descend.

2. An esterification column comprising horizontal plates shaped to hold liquids, each provided with a vapor pipe and a hood therefor to force ascending gases into liquids on said plates, storage plates alternating with the aforesaid plates, each.provided with apertures, with a tube or cylinder therein and pipes connecting the plates to let liquids descend, and a steam pipe at the bottom of the column.

3. An'apparatus comprising anesterification column comprising horizontal plates shaped tohold liquids, each provided with a vapor pipe and a hood therefor to .force ascending gases into liquids on said plates, storage plates alternating with the aforesaid plates, each provided with apertures, with a tube or cylinder therein and pipes connecting the plates to let liquids descend, a steam pipe at the bottom of the column, and a dephlegmator at the top.

4. An apparatus comprising an esterification column comprising horizontal plates shaped to hold liquids, each provided with a vapor pipe anda hood therefor to force ascending gases into liquids on said plates, storage plates; alternating with the aforesaid plates, each provided with apertures, with a tube orcylinder therein and pipes connecting the plates to let liquids descend, a steam pipe at the bottom of the column, and a combined dephlegmator and preheater at the top.

5. An apparatus comprising an esterification column comp-rising horizontal plates shaped to hold liquids, eachprovided with a vapor .pipe and a hood therefor to force ascending gases into liquids on said plates, storage plates alternating with the aforesaid plates, each provided with apertures, with. a tube or cylinder therein and pipes connecting the plates to let liquids descend, a steam pipe at the bottom of the column, a dephlegmator at the top, and a condenser connected to said dephlegmator.

6. An apparatus comprising an esterifica: tion column comprising horizontal plates shaped to hold liquids, each provided with a vapor pipe and a hood therefor to force ascending gases into liquids on said plates, storage plates alternating with the aforesaid plates, each provided with apertures, with a tube or cylinder therein and pipes connecting the plates to let liquids descend, a steam pipe at the bottom of the column, a combined dephlegmator and preheater at the top, and a preliminary mixing apparatus connected to the preheater.

incense 7 An esterification column comprising containing conduits,- and means for letting horizontal plates Y shaped to hold liquids, liquids descend from one plate'to another. said plates being provlded with vapor con- In testimony that I claim the foregoing, 10 7 duits and hoods to force ascendi gases into I have hereunto set my hand this 3rd day 5 liquids on said plates, storage p ates alterof September, 1919.

nating with the aforesaid plates, said stor-.

age plates being provided with apertures ARTHUR A. BAGKHAUS. 

